Patent Document 1 discloses a method for measuring the concentration of a substance using an electrochemical biosensor, in which an electrode containing an oxidoreductase, an oxidizing agent, and a buffer is used. In the measurement method, after allowing an enzyme reaction to substantially complete, a potential is applied between the electrode and a sample to measure a Cottrell current, and the concentration of the substance is measured based on the thus measured Cottrell current. Since the Cottrell current is affected by the diffusion of the substance, Patent Document 1 discloses the measurement of a diffusion controlled current, in terms of reaction kinetics. On the other hand, Patent Document 2 discloses a method in which the concentration of a substance is measured by detecting a current resulting from the charge transfer process, not the diffusion process of the substance, and measuring the concentration of the substance based on the detected current. Since this method allows for measuring the concentration of a substance without being affected by the diffusion, it is possible to carry out the measurement with a lower cost and shorter time, as compared to the method disclosed in Patent Document 1.